Atrial fibrillation is a form of arrhythmia, or irregular heartbeat, in which the atria (the two small upper chambers of the heart) quiver instead of beating effectively. While there are a number of variations of atrial fibrillation with different causes, they all involve irregularities in the transmission of electrical impulses through the heart. As a result of abnormalities in the heart's electrical impulses, the heart is not able to pump the blood out properly, and it may pool and clot. If a blood clot moves to an artery in the brain, AF can lead to stroke. AF is also associated with increased risks of congestive heart failure and cardiomyopathy. These risks warrant medical attention for patients with AF even if the symptoms are mild. Atrial fibrillation is the most common sustained heart rhythm disorder and increases the risk for heart disease and stroke, both leading causes of death in the United States. Over 2 million adults in the United States have been diagnosed with atrial fibrillation.
Various ablation techniques have been proposed to treat atrial fibrillation, including the Cox-Maze procedure, linear ablation of various regions of the atrium, and circumferential pulmonary vein ablation. Each of these techniques has its various drawbacks. The Cox-Maze procedure and linear ablation procedures are tedious and time-consuming, taking up to several hours to accomplish endocardially. Circumferential ablation is proving to lead to rapid stenosis and occlusion of the pulmonary veins, and of course is not applicable to treatment of the septal wall of the left atrium. The catheter mounted electrode arrays described in our co-pending patent application Kunis, et al., Atrial Ablation Catheter and Method of Use, U.S. application Ser. No. 10/997,172 filed Nov. 22, 2004 provide for more efficient and effective treatment of atrial fibrillation. The treatment of the septal wall is facilitated with the devices and methods described below, which permit septal wall treatment from a percutaneous venous access route without the need to maneuver a distally facing electrode array in apposition to the septal wall.